1. Field of the Invention
This invention relates to an injection molding machine for processing synthetic materials provided with a mold closing unit comprising a stationary mold carrier and a movable mold carrier, arranged to receive the parts of a mold between them and interconnected by force transmitting means, comprising at least two levers, substantially arranged transversally with respect to the closing direction. The levers are interconnected by connecting means, which are arranged at different distances from an injection axis, laid through the coupling points of the levers and nearly parallel with respect to the closing direction. Furthermore this arrangement comprises a closing device adapted to transfer the movable mold carrier in and out of a closed position with the stationary mold carrier and a device for applying the closing forces.
2. Description of the Prior Art
An injection molding machine of this type is known from U.S Pat. No. 4,222,731. In this machine the stationary mold carrier and the movable mold carrier are interconnected by a lever system, which comprises two levers in a vertical position and one horizontally disposed longitudinal beam, which is jointedly connected with the levers. Opposite to the longitudinal beam a further joining element is arranged in a larger distance from the closing axis, which is constituted by a piston-cylinder assembly. A lever provided for closing the mold, which is coupled at the movable mold carrier axially moves the movable mold carrier in a closing direction via a second piston-cylinder assembly. After the mold has been closed, the piston-cylinder assembly arranged at the lower end of the levers is used for applying the closing force. This way the object to create a mold clamping space without beams is certainly accomplished, however, forces are led into the machine base via the stationary mold carrier and the coupling of the second piston-cylinder assembly in the vicinity of the mold clamping space in such a way, that the machine base is subject to deformations, which cause inaccuracies during the mold closure and thus inexact injected pieces. Since the injection molding unit is displaced together with the movable mold carrier, the deformations are additionally reinforced. The application of a hydraulically driven piston-cylinder assembly causes problems with respect to the supply with hydraulic medium due to its movable arrangement.
Furthermore German Patent 39 24 182 discloses a blow molding machine, in which a force framing surrounds the two mold parts. When a drive for applying the closing forces is actuated, the whole framing is moved and the two movably supported mold carriers are directed against each other by a synchronizing device. In so far a decoupling between force transmission and guidance is effected, however, no reproducible mold closure can be obtained due to the movability of both mold carriers. Reproducible mold closure is required for the injection molding, since the forces occurring are essentially higher than those occurring during blow molding.